As is described in U.S. Pat. No. 8,221,064 to CNH America LLC, which is incorporated by reference in its entirety and for all purposes, a cleaning system for a combine harvester includes a fan assembly that is configured to blow air through reciprocating sieves to carry lighter elements of material other than grain (MOG) or chaff away.
Transverse or cross-flow fans of various designs have been advantageously employed with agricultural combines to provide the air that is blown upwardly and rearwardly through the sieves to carry the chaff away from the grain and tailings deposited onto the cleaning system sieves. Transverse fans are useful in combine cleaning systems because such fans can produce a wide stream of air that can be directed upwardly toward the cleaning sieves of the combine cleaning systems but require relatively little space. Such fans, in typical agricultural combines, are disposed such that their air outputs are below the sieves of the cleaning system.
One problem with long and wide transverse fans is that the air blowing through the fan housing will receive air through its inlet in a uniform manner, however, as the air stream passes through the fan housing, the air stream converges towards the center of the housing and creates a significantly stronger airstream in the center of the housing as compared with the sides of the housing. In other words, the air can be unevenly distributed along the width dimension ‘W’ of the fan (see FIG. 3A) as it travels from the inlet to the outlet of the fan. Moreover, in a situation where the crop mat becomes uneven across the width of the sieves, the air within the fan housing will typically follow the path of least resistance, namely, toward the unobstructed portion of the sieves. This may be referred to in the art as a blowout condition.
It would be desirable to provide uniform distribution of air across the entire width of the fan assembly in order to improve cleaning efficiency, crop processing, and either limit or prevent a blowout condition.